Spray cooling normally solid fatty acid hydroxy esters



April 7, 1953 H. D. ALLEN EI'AL 2,633,604

SPRAY COOLING NORMALLY SOLID FATTY ACID HYDROXY ESTERS Filed May 21, 194'? renditions 10f spraying.

Patented Apr. 7, 1953 1521M! LCQDIZI GNORMALLY i QLIDEATTX "AGID ,HYDROXY ESTERS filiaroldzllwaineiA-llen, Gl nzltock, mind Glar ence J s n, Arrows ithlliroolslyn,.N-.Xseasrsign rs 4 lGol at wRalm livaPeet rfiontnanr, l. ersey..l'2 tx,;N-.J.-na rporation of Delaware .Anplication MayI-Ql, 1947, Serial Non749f38 ."2 illaims- 1 invention relates to :processes ,;for :th

prep ration oflnormally :solid :tatty acid .hydroxy posters in particle "form by spray eoooling.

tIt-is an object of :this invention-:to-providean improved method forithe preparationnf normally rsolidrhydroxy esters of --fatty :acids :in particle :iormrby :spray cooling.

..;It is atfurther object iQflthiS :invention to proivide 'ayprooessgforysuch preparation of normally @solidjatty zacidihydlioxy :esters in particle form ":whichis characterized bygimprovedefiiciency of ,;heat transfer and capacity rfornhandling rela- -tively :la-rge amounts of material. I

It is ;-.a.-still "further'qobl'ect of this 7 invention to provide amethod for the spray cooling of fatty acid hydroxy esters wherebythe average size of the resultant product may be sim ly -;and efifectively controlled to conform substantially with predetermined size limitations.

Further objects and advantages of 13116 present invention will be apparent from the accompany- .ingtdescription and drawing.

,Theprocess of the present invention comprises spraying molten normally solid 'fatty acid hydroxy esters of polyhydric alcohols into a current of moving gas which serves the dual ,function-of cooling and solidifying .the molten esters ,and of separating the sprayed material as to v :the ipe B al a suitable rate, withthe .yalve gm open, land is divest d -.Qf sol d rei n substances inpassin throush strain r i Th pump 14, which is of thepositive-displacement type, serves .to elevate the fluid pressure in .the line, :and is provided with a by -pass line it and relief valve 1-8 for regulating line pressure .onthe discharge ,side of the pump. Heat exchanger is included in thesystem for the purpose of maintaining the 7 material to be sprayed at substantiallyiconstant t mperature seas-toassist;in;ins.unng consist nt anion .learineitheiheat eroha ser "thefiuid aura-i i2 aeri :iscdeliyeredrithrougheripe .22 tosp ayinozzle 24, whereupon it is divided into line oplets ;.and.;;disnersed::into ith zinterio :Q -th vfiltt cylindrical, elon ate spray zltower :26.

Air Qr other suitabl iaseous coo ;ne :med nm lisutnized to cool and s lidify e droplets =-9 fluid which issue-from ,thespraynozzle. -Whenever the following discussion is limited ate-the :use of air-as a coolingmedium', itristobannderstood that otherrelativelyrinert gases and gaseous mixtures are equally adapted .to .the: function .of cooling the sprayed esters.

In operation of the apparatus, -.cool-zairis:,-introduced into the bottom of thespray-tower'and caused .to flow upward through the tower, the sprayed ester moving downward through ,--the-air and being cooled thereby. It1wil1 -,be noted that theair, in travel suchapathis subjectto substantial unidirectional flow. The term unidirectional, as usedhere, is inot-intended-gto mean streamline flowhas turbulent flow conditions are desired moreoften than not in. carrying out the process. The strong ,upwa-rd movementlofztheyair in this case ,serves, 1however, -,in addition --to increasing the coolin I efiect upon the sprayed ester, to entrain the finer particles of ester and carry them from the top of the "tower via-duct 28, whereby the mixture rofair land lines is;-conveyed to a centrifugal dust collector 39, and the "suspended fine particles ,of product .removed therefrom.

Air leaves the centrifugalseparator by duct 32 and enters the blower 34, which imparts increased pressure to the body oiair at its discharge duct 36, ,therebycausing motion of the air in the system, which may be controlled (by varying the energy input tothe blower. The duct 36 is providedwith adjustable dam ers, or registers 3.8 and 4.0, -for causing the air discharged ;from the v1compressor ,to .be wholly or partially returned .to the bottomof-the spraytow- .erthroush cooler 42 rand-ducts stand 44a, 91- 11 char ed at the dampers to the atmosphere. When damper M1 is closedawi'th damper. pe n, the com s r.dischar es-to the atmosphereand ,air is ,forced into the -;bottom of the column through open end 146 ,by atmospheric pressure. This mode of operationis carried out most ei- 'fectively when-the atmosphere is ,at a.;ternperature suificiently low to provide "the requisite cooling effect. V

W h n-atm spheric-;temperature is :sogzhighas to -=eive an inadequate zeoolingrefiect, ;0l.Wh8le it;iiS eflfiSiFfilbl. imflx.tlllemonling:leataiforexampleupon rh's llllflg xphlllii lllarrfl w siconditions 17in rview, athe portion in passing through cooler 42.

damper 38 may be maintained in a closed position, and damper 40 opened so as to subject the air to closed cycle conditions, the cooler 42 serving to extract heat from the air to bring it to a desired temperature before entering the tower. Conditions of operation may also be modified by leaving damper 40 open and opening damper 38 to such degree as to cause a desired mixture of atmospheric and recycled air to flow up through the tower.

It will be apparent to one skilled in the art that the control of the properties of the air entering the tower which is afforded in the present process makes possible conditions of air fiow ranging from near streamline to extreme turbulence, that high and'low initial air temperatures may be employed, and that by virtue of the adaptability to varying degrees of mixed flow of atmospheric and recycled air, humidity, and consequently specific heat of the cooling medium may toa considerable extent be predetermined.

Where the atmospheric air is excessively humid to an extent which is undesirable, partial recycling serves to reduce the humidity of the air in the tower by dehumidification oi the recycled Similarly, where excessive dehumidification takes place in 'the cooler under total recycling conditions, at-

mospheric air may be utilized to an extent necessary to increase the water content of the air to a desired degree. On dry days, direct humidification may be effected by placing humiditying means such as pans of water, saturated wicks or other vapor generators near the air entrance to 'the spray column, thereby supplying water to increase the capacity of the air for accepting heat from the ester to be cooled.

Average particle size may be controlled by altering the capacity or" the spray nozzle and the degree of pressure used in pumping the fluid ester, smaller nozzles and higher pressures yielding finer droplets. The sprayed material may be divided generally into three classifications as to size: that which falls between predetermined limits which define a desired size range, that which is undesirably large, and that which is undesirably small, the last often called fines, or dust.

Under single fluid atomizing conditions, which are preferred in the process, the proportion of oversize particles formed is relatively small, and the proportion of fines, or dust may vary, for

example from 5 to 50% of the material sprayed, in the case of certain products. In order that a product of a desirable size range be produced in the process, the air rate may be chosen so that all 7 or most undesirably small particles formed on spraying will be carried from the tower by the upward moving column of air. The desirable and oversize particles may then drop from the opening 46 upon the screen 48 which is caused'to'vibrate by vibrating mechanism 50.

Particles of the desired size may pass through the screen and be deposited thereby in finished product drum 52, while oversize material is not passed through and may descend the chute 59, which comprises'a unitary member with the screen -48, so as to be placed in drum 56 with material intended for remelting or for use where precision of product size is of little consequence.

Undersize particles which are carried upwards .2 from the tower with the air through duct 28 are separatediirom the: air in thecentrifugal separator 3ll,'and drop through column 56, being discharged through counterweighted gate 58 into drum 6!). The fines thus collected may be remelted or used where size is not critical, as in the case of oversize material. In some cases it may be particularly desirable to produce an extra fine product, in which event rates and critical variables of the process may be adjusted so as to produce a maximum of fines which may be collected in drum 6D, with all other products being remelted or otherwise disposed of. It is also possible to produce, in one operation, several size classes of sprayed material, each of which may constitute a satisfactory range for various purposes.

Where the process is carried out as herein described, under conditions of well-balanced equilibrium, it may be seen by those skilled in the art that zones are formed in which cooling of the fluid ester, solidification of the ester and cooling of the solid ester take place. Adjustment of air flow and spraying rate, as described, may be utilized to cause the zones to occupy the desiredrelative volume proportions of the tower for maximum heat transfer efiiciency, and the desired separation of fines.

While the discussion here has been limited to the use of a system employing counter current flow conditions, the process is not limited thereto, and parallel flow may be utilized effectively in carrying out the method of the invention. The apparatus shown in the figure may be altered so as to carry out the process under conditions of parallel, or concurrent fiow by interchanging ducts 23 and Ma with respect to entrance to the tower, and by simply providing suitable bafile plating at the point where the air leaves the bottom of the tower in order to prevent excessive entrainment of the product with the exit air, while nevertheless effecting the desired separation of the fines from the larger sized material.

A simple and efifec'tive construction for accomplishing parallel flow cooling by modification of the apparatus shown in the drawing comprises an arrangement in which communication is provided between the bottom of the tower and the inlet side of the centrifugal separator 38 by an annular chamber surrounding but not obstructing the open end of the tower, and inwhich communication is provided by means of a duct between the top of the tower and the cooler 42.

The nozzle pressure used in carrying out the present invention may vary from to 200 pounds per square inch, gage, for best results, depending upon the material to be sprayed. The air velocity may preferably vary between 300 and 600 feet per minute. It is generally preferred that the ester be introduced to the spray nozzle at a temperature slightly above its melting point.

The parallel fiow technique of operation is generally preferred in the case of materials which are subject to decomposition or other deleterious effects when subjected to high temperatures in molten condition, and may be used with particular advantage where it is desired to reduce the temperature of the molten material rapidly so as to forestall such undesirable effects.

An example of the invention is included describing typical practice in accordance with the invention, and is included to illustrate and not to limit the invention:

Under countercurrent spraying conditions, in an apparatus of the type shown in the drawing, 450 pounds per hour of glyceryl' monosteai'ate Percent Through 20 mesh 35 Through 40 mesh 55 Through 60 mesh Finer than 60 mesh 5 Of three additional runs, the amount of fines expressed as percent of the total feed were as follows for the air rates given:

Air rate Fines, percent 2300 cubic feet per minute 46 1900 cubic feet per minute 17 1500 cubic feet per minute 7 Having thus described a limited number of forms of our invention, it should be understood that we do not wish to be narrowly bound except as defined in the appended claims.

We claim:

1. The process which comprises spraying molten, normally solid fatty acid hydroxy ester in fine droplet form into a current of moving gas at lower temperature to cool and solidify the ester, the contact of the respective materials forming zones of cooling and solidification, and the rate of motion of the gas being such as to carry undesired small particles therewith away from said zones.

2. The process of producing normally solid fatty acid hydroxy esters in particle form of predetermined range of sizes which comprises pumping a stream of said esters which are at a temperature only slightly above the solidification point under controlled pressure to a nozzle adapted to divide said stream into molten droplets which are predominantly within said size range, contacting said droplets as soon as formed with a current of humid air at lower temperature to solidify said droplets, and utilizing said current of humid air to effect classification of solidified particles into fractions of predetermined range of sizes.

HAROLD DWAINE ALLEN. CLARENCE JOSEPH ARROWSMITH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,603,559 Schwantes Oct. 19, 1926 1,734,260 Lamont Nov. 5, 1929 1,785,533 Schwantes Dec. 16, 1930 1,837,869 Jewett et a1. Dec. 22, 1931 

1. THE PROCESS WHICH COMPRISES SPRAY MOLTEN, NORMALLY SOLID FATTY ACID HYDROXY IN FINE DROPLET FORM INTO A CURRENT OF MOVING GAS AT LOWER TEMPERATURE TO COOL AND SOLIDIFY THE ESTER, THE CONTACT OF THE RESPECTIVE MATERIALS FORMING ZONES OF COOLING AND SOLIDIFICATION, AND THE RATE OF MOTION OF THE GAS BEING SUCH AS TO CARRY UNDESIRED SMALL PARTICLES THEREWITH AWAY FROM SAID ZONES. 